Tagging of η mesons using the pd → 3Heη reaction near threshold

A zero-degree spectrometer for tagging η mesons on the CELSIUS/WASA facility is described, and its characteristics are presented. Tagging of η mesons is performed by detecting ³He ions produced by reaction pd → ³Heη close to the production threshold. The low background level (<2%) is in good agreement with the data obtained earlier on the SATURNE accelerator.     

Empirical assessment of a threshold model for sylvatic plague.

Plague surveillance programmes established in Kazakhstan, Central Asia, during the previous century, have generated large plague archives that have been used to parameterize an abundance threshold model for sylvatic plague in great gerbil (Rhombomys opimus) populations. Here, we assess the model using additional data from the same archives. Throughout the focus, population levels above the threshold were a necessary condition for an epizootic to occur. However, there were large numbers of occasions when an epizootic was not observed even though great gerbils were, and had been, abundant. We examine six hypotheses that could explain the resulting false positive predictions, namely (i) including end-of-outbreak data erroneously lowers the estimated threshold, (ii) too few gerbils were tested, (iii) plague becomes locally extinct, (iv) the abundance of fleas was too low, (v) the climate was unfavourable, and (vi) a high proportion of gerbils were resistant. Of these, separate thresholds, fleas and climate received some support but accounted for few false positives and can be disregarded as serious omissions from the model. Small sample size and local extinction received strong support and can account for most of the false positives. Host resistance received no support here but should be subject to more direct experimental testing.     

Reibungsversuche mit Krypton bei niedrigen Drücken

Tests of a linear Equation on the Evaluation of Krypton Friction Experiments at low Pressures and Connections to Viscosity Effects The coefficient of viskosity is nearly constant in the region with STP conditions and is independent of the pressure. This coefficient decreases with lowering the pressure until the region of molecular flow is reached. There we have free molecular‐ or vacuum viscosity. Experiments with the friction of gas have to take in the gas between surfaces which are movabel and parallel. Reactions of the gas with the moving surface cannot be neglected. We made our lab‐examinations of gas friction effects between two rotating cylinders. Generally there is a linear equation of the reciprocal values of viscosities and pressures. Our experiments show a region, where this linear relation is valid. This region has a low limit with coming to molecular flow and an upper limit if the gas is warmed up by friction at higher pressures.     

Plasma spraying of zircon

Zircon, ZrSiO₄, is a natural mineral used for various applications as a refractory bulk material. It is an excellent feedstock for the plasma spraying of protective coatings and free-standing bodies. Zircon decomposes on spraying into t-ZrO₂ and glassy SiO₂, which can be preserved in deposits by fast cooling. This combination of zirconia and silica exhibits properties such as a high thermal shock resistance, good corrosion resistance, low wettability, etc. The final properties of deposits can be further enhanced by the addition of other materials such as alumina. For instance, alumina-zircon plasma-sprayed free-standing pipes have a low gas permeability. Several technical applications are discussed.     

Direct synthesis of epitaxial zinc sulphide layers on zinc single-crystal substrates

Epitaxial thin zinc sulphide layers have been grown by direct synthesis on the basal face of zinc single crystals. Sulphur vapour reacted on the surface of the crystals, which were grown in sealed glass ampoules evacuated to 10^?6 torr. The thicknesses of the layers investigated varied from several hundred to 1000–1500 Å. The morphology, structure and epitaxy of the films were examined by electron microscope, electron and X-ray diffraction techniques. It was found that the film lattice had a sphalerite-type cubic structure, the perfection of the layer structure increasing with rise in both the substrate temperature and the sulphur vapour pressure. The layers were produced at substrate temperatures of 250°–400°C: polycrystalline ZnS films were obtained in the range 250°–300°C; at higher temperatures a definite texture gradually appeared and above 370°C, with a sulphur vapour pressure of 0.2–10 torr, the films became epitaxial. The following epitaxial relation was established:

$\text{{111} ZnS ∥ {0001} Zn}$

with

$\text{<110 > ZnS ∥ <11}\text{20}\text{> Zn}$

The zinc sulphide films reproduced the surface structure of the supporting zinc single crystals very well and could conveniently be used as electron microscope replicas.     

Hypertension and left ventricular mass index (L.VMI) in patients on regular hemodialysis (RDT)

Background:  Because of high incidence of acquired renal cyst and renal malignancy, it is suggested that spontaneous renal rupture more frequently occurs in patients receiving long‐term hemodialysis than in the general population. This study was performed to evaluate the clinical characteristics of spontaneous renal rupture in hemodialysis patients. Methods:  This retrospective study enrolled 12 hemodialysis patients who developed spontaneous renal rupture. We investigated primary renal disease, duration of dialysis, clinical symptoms and signs, radiologic findings, treatment modalities, and histologic findings. Result:  The mean age of the patients was 54 ± 10 years old and the number of male was 9. Primary renal disease consisted of autosomal dominant polycystic kidney disease (PCKD)(n = 5), chronic glomerulonephritis (n = 2), diabetic nephropathy (n = 1), hypertensive nephropathy (n = 1), unknown cause (n = 3). Presenting symptoms and signs were sudden onset of flank pain in 9 patients and gross hematuria with mild flank pain in 3 patients. Mean duration from initiation of hemodialysis to development of spontaneous renal rupture was 53 ± 36 months. Abdominal computed tomography showed subcapsular or perinephric hematoma in all patients. Of the 7 non‐PCKD patients, 6 patients had multiple acquired renal cysts. Surgical exploration was undertaken in 9 patients. Pathologic examination demonstrated small sized renal cell carcinoma in 2 of 9 patients. Three patients were only treated with conservative management including blood transfusion. All 12 patients recovered without recurrence. Conclusion:  This study demonstrated that genetic or acquired renal cyst was an important cause of spontaneous renal rupture in hemodialysis patients and presenting manifestations were sudden onset of flank pain and gross hematuria.     

On the SO2 problem of solid fuel combustion

Many companies use two-phase absorbents (CaCO₃ suspension) for waste gases purification from SO₂. A qualitative theoretical analysis of the absorption kinetics in the cases of two-phase absorbent, using the convection-diffusion type of model, is presented. It is shown that the low CaCO₃ concentration lead to very small chemical reaction rate and as a result the absorption rate is limited by the physical absorption of SO₂ in water, i.e. the process efficiency is very small. An average concentration model for quantitative analysis of the absorption process and an iterative numerical algorithm for the model equations solution is proposed.